Influence of Roughness on Nondestructive Characterization of Interconnect Film Mechanical Properties by Surface Acoustic Wave

Surface acoustic wave (SAW) technology is a new nondestructive and fast on-line testing technology for mechanical properties of interconnect films. The theoretical dispersion curves of SAWs propagating on the film/substrate structure are calculated by the Green's function and matrix method, assuming that the film surface and interface are smooth. In this paper, the random rough curves of the film surface and interface are simulated by the Monte Carlo method. The dispersion curves considering the surface and interface roughness are calculated by the finite element method. The dispersion curves obtained from ideal SAW model and roughness model are compared. This study indicates that the influence of surface and interface roughness on the determination of mechanical properties for SiO ₂ film and low-k film by SAW method is small, and it can be ignored.